1. Field of the Invention
The present invention relates to a video signal processing apparatus, and more particularly to a video signal processing apparatus capable of processing video signals having different aspect ratios.
2. Related Background Art
The aspect ratio of a conventional television signal is 3:4, whereas a high definition television signal has an aspect ratio of 9:16.
A so-called wide monitor is available in the market which converts a Hi-Vision signal into an NTSC signal and displays it on a wide screen having the aspect ratio of 9:16 by using the NTSC method.
It is convenient to superpose a discrimination signal between the aspect ratios 3:4 and 9:16 on a video signal to allow a monitor to automatically judge the aspect ratio.
A method has already been proposed in which aspect ratio digital information (hereinafter called an aspect ID) is superposed on the twentieth and two hundreds and eighty third lines of the video signal during the vertical blanking period.
There are monitors requiring the aspect ID and monitors not requiring it.
An image processing apparatus for the aspect ratio 3:4, as well as an image processing apparatus for the aspect ratio 9:16 has already been developed. However, these image processing apparatus cannot process video signals having different aspect ratios.
A video signal processing apparatus capable of processing video signals having different aspect ratios has been long expected.
The following points should be taken into consideration when such a video signal processing is intended to be realized.
For example, as the application of selective synthesization of a plurality of video signals, there are known image switching, wipe, scroll, cross fade, picture-in-picture, and the like.
A conventional video signal processing apparatus performs selective synthesization of a plurality of input video signals, with no consideration of a difference between aspect ratios of the video signals.
In the case of a VTR as the video signal processing apparatus, a synchronization signal which is to be essentially superposed on a reproduced video signal may sometimes be lost or may become unstable during a specific reproduction process (such as high speed search reproduction, slow reproduction, and still image reproduction). In such a case false horizontal or vertical synchronization signal has been generated conventionally. Also in a conventional VTR, cutting pulses are not provided within vertical synchronization pulses.
If there is no cutting pulse on the vertical synchronization pulse, it is not possible to correctly count the twentieth and two hundreds and eighty third lines during the vertical blanking period, and therefore to detect the aspect ID. Or a multiplied character signal recorded after and before the aspect ID is erroneously detected.
In such a case, the wide monitor receives a video signal with the aspect ratio 9:16 as a video signal with the aspect ratio 3:4 and displays it with the aspect ratio 3:4.